As is well known, the diamond which is a crystal of carbon has been used for a variety of applications owing to its very high hardness, excellent resistance against abrasion as well as excellent slipping property, heat conductivity and high refractive index. For instance, it has been used for the tools for cutting, such as cutting tool, end mill and file, metal molds for plastic machining, such as punch and dies, sliding members such as valve lifter and bearing, heat-radiating members such as heat sink, electronic circuit boards and optical parts such as lens and window.
In order for their properties to be exhibited to a sufficient degree, these diamond products must have the diamond-surface polished to assume smooth surface.
The diamond-surface had so far been mechanically polished by using grains or a grind stone of diamond requiring extended periods of time. Besides, since both of them are abraded, there occurred such problems as short life of the tool and not being suited for polishing rugged three-dimensional surfaces. In an effort to improving the above defects, therefore, various kinds of polishing methods have now been proposed.
A patent document 1, for example, proposes a polishing method which conducts the polishing by using a polishing member constituted by a metal that easily reacts with carbon in the diamond crystals, applying ultrasonic waves onto the polishing member, and pushing the polishing member onto the surfaces of the diamond while the polishing member is undergoing ultrasonic oscillation. Here, examples of the metal that easily reacts with carbon include a γ-Fe-containing stainless steel, titanium (Ti), zirconium (Zr) and tantalum (Ta).
A patent document 2 proposes a polishing method by using, as a grind stone, an intermetallic compound of at least one metal element selected from the group consisting of Al, Cr, Mn, Fe, Co and Ni and at least one metal element selected from the group consisting of Zr, Hf, V, Nb, MO, Ta and W, and pushing the grind stone onto the diamond-surface that is moving relative thereto while, as required, heating the grind stone at 100 to 800° C.
A patent document 3 proposes a method of polishing the diamond-surface by focusing the laser beam on the diamond-surface.
A patent document 4 proposes a method of polishing a diamond film by sliding a metal and the diamond relative to each other at a point where the two are contacting to each other while continuously varying the temperature over a range of 700° C. to 1000° C. at the portion where the metal and the diamond are contacting to each other.